The present invention is concerned with stabilized fertilizer solutions in which the crystallizing out of certain components is prevented by use of water soluble organic polymeric compounds as a stabilizer.
An effective nitrification inhibitor in nitrogen fertilizers is, for example, dicyandiamide, its use in liquid fertilizers being of especial interest. A high effectiveness of the nitrification inhibition is achieved when the amount of dicyandiamide nitrogen accounts for about 10% of the total amount of nitrogen in the fertilizer. In the case of nitrogen fertilizers based on ammonium nitrate-urea, this amount of dicyandiamide easily remains in solution at temperatures down to about 20.degree. C. but, upon cooling to temperatures of 10.degree. C. and below, within a short time, dicyandiamide crystallizes out as crystals--rapidly growing to a size of 1 mm. or more--with concurrent lose of dissolved dicyandiamide from the solutions. As fertilizer solutions are applied by spraying or sprinkling, a practical problem arises with the separation of large crystals of dicyandiamide, namely conduit pipes, sieves and nozzles are rapidly blocked. Considering that nitrogen fertilizer solutions are preferably used in the early part of the year, during which time, in northern latitudes, very low outside temperatures still prevail, the problems with crystallizing out of dicyandiamide are often encountered in practice, especially when the solutions have been stored over the winter.
Thus, it is an object of the invention to provide stable fertilizer solutions in which the crystallization of dicyandiamide is prevented over long periods of storage and/or cooling.